Six Engine rebuilds in 100miles !!!
#1
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Help, Desperation, any ideas warmly welcomed, are we missing something??
My mid my02 Sti never went well, I know because I had a Prodrive WRX 2002 before and it was significantly quicker. So off I went to Rally Star the South African Subaru tuning specialists.
They recommended and fitted a Unichip and Bosal 76mm decat system.
We should have noticed this at the time but on the 'before mod' Dyno run the ECU was permanently in limp mode, we put this down to poor octane fuel. We only get 93RON on a good day in J'burg.
With the pipe and chip fitted we were getting 180Kw uncorrected-at-the-wheels and all appeared good (that’s 240bhp) running between 1.2and 1.3bar.
On the way home it missed twice and knocked a hole in Number three. By the way this level of tune has been done to many SA Sti's without any problem.
On stripdown No3 appeared lean (lighter colour than the others) and the fuel pump was suspected as we had had pumps fail before due to African dirty fuel, usually after 50k kms or so. The pump was checked and sure enough although it was producing around 4bar it was a little slow getting there. The rebuilt engine went back in, it looked good on the Dyno and a friend delivered the car back to me in Botwana, Next day I gave it a try running 98RON and guess what - a hole in No3.
Since then its never done more than 25miles, once it blew up on the dyno.
To cut a long story of engine rebuilds and replacement subs short, this is what has been done,
Changed injectors.
Fitted second fuel pump -gives up to 5bar.
Changed MAF sensor and both Lambda sensors.
Changed fuel regulator. ECU,
Fitted another Fuel rail with yet another different set of Sti injectors.
Changed Absolute Manifold pressure sensor.
Fitted new Sti inlet manifold.
Heads pressure tested.
Changed Engine wiring harness after finding a slightly loose pin on No3 injector. (thought we found it that time)
Checked over and over for boost leaks.
Ran all the SA available Subaru diagnostics-no fault found.
In fact the only sensor not changed is the cam position sensor- but that couldn't cause lean running could it?
Still even mapped as rich as possible with all the above done it blew no3 again.
Last thing we have done is de chipping and restored original pipe with everything back to standard.
So back to square one, it runs in limp mode all the time even on 102.3RON race fuel and 13.7AFR which seems lean?? with two different standard Sti ECUs but fails to destroy no3 piston like this although it now slaps a bit.
I'd take it back to Subaru under warranty but now they know it was modified, because of the loan of Factory test gear etc. so I don't expect much help there, I hope I'm wrong.
What is this little problem??
We are now changing the ECU to engine harness out of even more desperation.
What is it???? All sympathy and sensible suggestions appreciated.
PS I have to say RallyStar have been absolutly incredible in their efforts to solve this problem even though they haven't.
My mid my02 Sti never went well, I know because I had a Prodrive WRX 2002 before and it was significantly quicker. So off I went to Rally Star the South African Subaru tuning specialists.
They recommended and fitted a Unichip and Bosal 76mm decat system.
We should have noticed this at the time but on the 'before mod' Dyno run the ECU was permanently in limp mode, we put this down to poor octane fuel. We only get 93RON on a good day in J'burg.
With the pipe and chip fitted we were getting 180Kw uncorrected-at-the-wheels and all appeared good (that’s 240bhp) running between 1.2and 1.3bar.
On the way home it missed twice and knocked a hole in Number three. By the way this level of tune has been done to many SA Sti's without any problem.
On stripdown No3 appeared lean (lighter colour than the others) and the fuel pump was suspected as we had had pumps fail before due to African dirty fuel, usually after 50k kms or so. The pump was checked and sure enough although it was producing around 4bar it was a little slow getting there. The rebuilt engine went back in, it looked good on the Dyno and a friend delivered the car back to me in Botwana, Next day I gave it a try running 98RON and guess what - a hole in No3.
Since then its never done more than 25miles, once it blew up on the dyno.
To cut a long story of engine rebuilds and replacement subs short, this is what has been done,
Changed injectors.
Fitted second fuel pump -gives up to 5bar.
Changed MAF sensor and both Lambda sensors.
Changed fuel regulator. ECU,
Fitted another Fuel rail with yet another different set of Sti injectors.
Changed Absolute Manifold pressure sensor.
Fitted new Sti inlet manifold.
Heads pressure tested.
Changed Engine wiring harness after finding a slightly loose pin on No3 injector. (thought we found it that time)
Checked over and over for boost leaks.
Ran all the SA available Subaru diagnostics-no fault found.
In fact the only sensor not changed is the cam position sensor- but that couldn't cause lean running could it?
Still even mapped as rich as possible with all the above done it blew no3 again.
Last thing we have done is de chipping and restored original pipe with everything back to standard.
So back to square one, it runs in limp mode all the time even on 102.3RON race fuel and 13.7AFR which seems lean?? with two different standard Sti ECUs but fails to destroy no3 piston like this although it now slaps a bit.
I'd take it back to Subaru under warranty but now they know it was modified, because of the loan of Factory test gear etc. so I don't expect much help there, I hope I'm wrong.
What is this little problem??
We are now changing the ECU to engine harness out of even more desperation.
What is it???? All sympathy and sensible suggestions appreciated.
PS I have to say RallyStar have been absolutly incredible in their efforts to solve this problem even though they haven't.
#3
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Originally Posted by WUZ
I would have thought 12.8:1 is OK on idle but on boost you'll be looking for 11.2-11.5:1
Russell
Russell
#5
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Originally Posted by WUZ
The ECU is controlling injectors pulse at idle to get the AFR that is programming tells it that it needs!
13.7:1 is not that lean at all (when at idle!)
Russell
13.7:1 is not that lean at all (when at idle!)
Russell
Chris
#6
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I once had a problem with the standard subaru fuel rails under the manifold, there were massive fuel pressure differences between one side of the rail to the other, mainly because where the pipes bend they get flattened or could be a fuel blockage. Try parallel fuel rails from MRT or APS. Each fuel rail is fed from a centralised distribution block and the return is T'd up into the FP regulator. At least you will ensure the same amount of fuel is getting to each bank of cylinders.
Hope this helps
Conrad
PS Nice part of Africa
Hope this helps
Conrad
PS Nice part of Africa
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#7
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Originally Posted by Conrad_Bradley
I once had a problem with the standard subaru fuel rails under the manifold, there were massive fuel pressure differences between one side of the rail to the other, mainly because where the pipes bend they get flattened or could be a fuel blockage. Try parallel fuel rails from MRT or APS. Each fuel rail is fed from a centralised distribution block and the return is T'd up into the FP regulator. At least you will ensure the same amount of fuel is getting to each bank of cylinders.
Hope this helps
Conrad
PS Nice part of Africa![Wink](https://www.scoobynet.com/images/smilies/wink.gif)
Hope this helps
Conrad
PS Nice part of Africa
![Wink](https://www.scoobynet.com/images/smilies/wink.gif)
Thanks for the suggestion Conrad, We are measuring fuel pressure on the return side so there should be plenty of fuel available. Its always the No3 that lets go so obviously its still that one getting less fuel. But the basic problem remains, why don't we get enough fuel?? Am now thinking to try a separate supply eliminating the tank to engine and return plumbing to see if that does anything for us. After all pressure ain't the same as flow, could be bubbles?
And yep Bots is a well kept secret, not half bad and NO SPEED CAMERAS! although they do have hand-helds.
Chris
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#9
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Originally Posted by Jolly Green Monster
have you used the same set of heads each time it has been rebuilt?
Wondering if there is valve problem on number 3..?
Wondering if there is valve problem on number 3..?
Any one ever looked at injector pulses on a scope? I'm thinking of trying that as well.
Chris
#12
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Originally Posted by Jolly Green Monster
you replaced the engine loom but have you replaced or added extra cable as a temporary measure from ecu to injector number 3?
#13
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Originally Posted by Conrad_Bradley
Measuring at the FPR doesnt show the difference in FP on one side of the engine to the other. Convert to parrallel fuel rails to be sure.
Chris
#17
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Originally Posted by P20SPD
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Even after 30k miles it blew a piston. we need to concentrate on AFR here, its lean running and detonation that makes holes in pistons
#19
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Originally Posted by P20SPD
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Assuming you have checkd the fuel pressure regulator?
No air leaks post MAF?
But now you got me thinking (doesn't happen often)
Why 13.7 AFR all the way from idle to 1Bar?? What controls the mixture- the MAF input to the ecu right? So we already changed the MAF maybe its a wiring problem from MAF to ecu. All along I've been looking at why No3 is always the one to go but Conrad is spot on with the fuel rail problem always making No3 leaner than the others so if the whole engine is lean it will always be No3 thatwill go first right?
Chris
#20
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Originally Posted by Botswana WRX
Yes replaced fuel pressure regulator and checked for air leaks everywhere.
But now you got me thinking (doesn't happen often)
Why 13.7 AFR all the way from idle to 1Bar?? What controls the mixture- the MAF input to the ecu right? So we already changed the MAF maybe its a wiring problem from MAF to ecu. All along I've been looking at why No3 is always the one to go but Conrad is spot on with the fuel rail problem always making No3 leaner than the others so if the whole engine is lean it will always be No3 thatwill go first right?
Chris
But now you got me thinking (doesn't happen often)
Why 13.7 AFR all the way from idle to 1Bar?? What controls the mixture- the MAF input to the ecu right? So we already changed the MAF maybe its a wiring problem from MAF to ecu. All along I've been looking at why No3 is always the one to go but Conrad is spot on with the fuel rail problem always making No3 leaner than the others so if the whole engine is lean it will always be No3 thatwill go first right?
Chris
Chris
#21
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Seems to me that you have the right idea when thinking its fuel pump related, it probably is BUT not the pump but the fuel pump controller, the oem ecu sets the pump duty at either 33, 66 or 100% dependant on engine load, if the controller is stuck in 33% mode then you would get the results described.
To prove this suggest hard wiring the pump directly to bypass the controller ie connect a switched positive feed in parrallel to the existing cct, that will run the pump at full chat all the time, it will over fuel abit on lighter loads but should fix the heavy load problem, if it does then replace the fuel pump controller and remove the bypass.
cheers
bob
To prove this suggest hard wiring the pump directly to bypass the controller ie connect a switched positive feed in parrallel to the existing cct, that will run the pump at full chat all the time, it will over fuel abit on lighter loads but should fix the heavy load problem, if it does then replace the fuel pump controller and remove the bypass.
cheers
bob
#22
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BTW on these cars No 3 is not leanest, no 1 is however no3 gets extra heat from turbo and at that afr would be sure to suffer.
FPR is adjacent no 1 not no 3 ie last in line is no 1.
Add to which if the ecu pulls timing big time over this then egt's will rise due to the retard in any case.
bob
FPR is adjacent no 1 not no 3 ie last in line is no 1.
Add to which if the ecu pulls timing big time over this then egt's will rise due to the retard in any case.
bob
#23
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Originally Posted by Bob Rawle
BTW on these cars No 3 is not leanest, no 1 is however no3 gets extra heat from turbo and at that afr would be sure to suffer.
FPR is adjacent no 1 not no 3 ie last in line is no 1.
Add to which if the ecu pulls timing big time over this then egt's will rise due to the retard in any case.
bob
FPR is adjacent no 1 not no 3 ie last in line is no 1.
Add to which if the ecu pulls timing big time over this then egt's will rise due to the retard in any case.
bob
Chris
Last edited by Botswana WRX; 25 November 2004 at 04:20 AM.
#24
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Originally Posted by Botswana WRX
Thanks for the info Bob, We do see the fuel pressure rising on the Dyno runs as it comes on boost and with the current uprated pump its up to 6bar so I don't think it can be the controller. Its just that FAR stays at 13.7ish instead of 11.5. and we have tried a new original ecu with no change.
Chris
Chris
Chris
#25
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why were you using a unichip when you can get far better control of the engine using EcuTek?
You need someone on that car who knows their stuff, doing live datalogs to see where the problems are. You could have a completely shot or badly remapped ECU.
Do you have a copy of deltadash to do some logging with?
You say you use 93RON, dont you mean 93PON? which is about 97RON.
You need someone on that car who knows their stuff, doing live datalogs to see where the problems are. You could have a completely shot or badly remapped ECU.
Do you have a copy of deltadash to do some logging with?
You say you use 93RON, dont you mean 93PON? which is about 97RON.
#26
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Originally Posted by johnfelstead
why were you using a unichip when you can get far better control of the engine using EcuTek?
You need someone on that car who knows their stuff, doing live datalogs to see where the problems are. You could have a completely shot or badly remapped ECU.
Do you have a copy of deltadash to do some logging with?
You say you use 93RON, dont you mean 93PON? which is about 97RON.
You need someone on that car who knows their stuff, doing live datalogs to see where the problems are. You could have a completely shot or badly remapped ECU.
Do you have a copy of deltadash to do some logging with?
You say you use 93RON, dont you mean 93PON? which is about 97RON.
#30
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No, but I guess African rodents could be a problem, what exactly is input to the ecu use to control the mixture apart from lambda to close the loop and injector pulse length and fuel pressure. Is it MAP to match the fuel pressure to maintain differential fuel to Manifold pressure and just MAF to decide if its Idle, cruise or boost, If thats the case I will try tempory wires between MAF and ecu. We may be getting somewhere, thanks.
Chris
Chris